Stephen J. Glick PhD, Presenter: Research grant, Toshiba Corporation Research collaboration, Kromek

Kesava Kalluri BS, Abstract Co-Author: Nothing to Disclose

It was observed that projection based weighting can provide up to 40% improvement in SNR compared to energy integrating detectors for breast CT.

In an effort to improve the early stage detection and diagnosis of breast cancer, a number of research groups have been investigating the use of x-ray computerized tomography (CT) systems dedicated for use in imaging the breast. For a number of reasons, the performance of energy integrating detectors are sub-optimal for use in CT imaging of the breast. It is expected that the next generation of x-ray detectors for digital radiography and CT will have the capability of counting individually measured photons and recording their energy. In this study, we evaluate improvements in image quality that can be attained using energy weighting photon counting detectors for breast CT. In addition, we determine the optimal energy thresholds for defining energy bins.

Previously reported models for the signal-to-noise ratio of weighted images were used to analytically explore optimal energy thresholds for a given breast CT measurement system. A background cylinder with 50% glandular, 50% adipose tissue was used with a centered contrast element modleing either microcalcification,  an infiltrating ductal carcinoma lesion, or a lesion with iodine uptake. A tungsten anode x-ray spectra with 50, 60, 70, and 80 kVp was studied. SNR values for a specified mean glandular dose were computed. In addition, the effect of errors in the optimal weights due to inaccurate estimates of lesion size and composition were studied.  

Projection based energy weighting can provide up to 40% improvement in SNR compared to the energy integrating detector. There seems to be little penalty in going to 3-5 energy bins from 1 keV bins. Optimal energy thresholds were computed for 3,4, and 5 bin energy windows and for the three material compositions. Energy thresholds for IDC and microcalcification were similar, but those for the iodine lesion tended to have one energy threshold at the K-edge of iodine. The SNR was only weakly dependent on the correct estimate of lesion size, however, using the correct lesion composition was important.

Glick, S, Kalluri, K, Optimal Energy Thresholds for Breast CT Using Photon Counting Detectors.  Radiological Society of North America 2011 Scientific Assembly and Annual Meeting, November 26 - December 2, 2011 ,Chicago IL. http://archive.rsna.org/2011/11011610.html